Suppression of superconductivity in high-T_c cuprates due to nonmagnetic impurities: Implications for the order parameter symmetry

摘要

We studied the effects of nonmagnetic impurities on high-temperature superconductors by solving the Bogoliubov-de Gennes equations on a two-dimensional lattice via exact diagonalization technique in a fully self-consistent way. We found that s-wave order parameter is almost unaffected by impurities at low concentrations while d_(x~2 - y~2) -wave order parameter exhibits a strong linear decrease with impurity concentration. We evaluated the critical impurity concentration n_i~c at which superconductivity ceases to be 0.1 which is in good agreement with experimental values. We also investigated how the orthorhombic nature of the crystal structure affects the suppression of superconductivity and found that anisotropy induces an additional s-wave component. Our results support d_(x~2-y~2)-wave symmetry for tetragonal and s + d_(x~2-y~2)-wave symmetry for orthorhombic structure.